I've pulled apart the theme that came with my PocketBook 360 plus. Most of the resources in the theme are 4-bit 16 gray scale images, but the pbres program doesn't handle 4 bit images. There are some methods in libinkview, like LoadBitmap and SaveBitmap, but I don't see any way to make them create the higher resolution resources.

I've created my own theme compiler program and with luck may be able to do something eventually, since it doesn't seem hopeful that PocketBook will provide us with an updated theme compiler soon.

Meanwhile, I've bundled the 360 plus default theme up for those who want to play with it. It includes a list of the resources in the pbt, the config file, the bmp files that were produced by libinkview's 'SaveBitmap', and some binary itbitmap resources (as .pbr files). My theme compiler will compile from the ibitmap resources, bmp, or png, so if somebody is feeling adventurous I will send the code for the theme compiler privately. I don't want to upload it yet because it's not quite ready for public use.

The previously posted BMP files for the 360 plus default theme did not include the transparent colors from the mask, because the SaveBitmap function didn't do that. Here is an updated package for the 360 default theme which includes transparent colors.